Install C2ME on your Fabric server

C2ME, short for Concurrent Chunk Management Engine, is a Fabric mod that speeds up chunk generation, chunk saving and chunk loading by spreading the work across several CPU cores. It runs on the server, and Modrinth lists the client side as optional, so your players don't need to install it.

Checked against C2ME 0.4.2-alpha.0.106 for Minecraft 26.3 on Fabric, October 2026.

What it needs

C2ME for Minecraft 26.3 needs Fabric Loader 0.18.3 or newer, Java 25 and a Minecraft version newer than 1.21.11. The panel runs Minecraft 26.x on Java 25 and handles that for you. This build does not list Fabric API as a dependency.

The Fabric build is the one covered here. C2ME has a separate NeoForge project, and a Paper or Purpur server can't load it because it is a mod, not a plugin.

The project fully supports only the latest Minecraft release and the latest snapshot. Older releases get long-term support and critical fixes only.

Look for Mods under Content in the panel menu. If the tab says Plugins or is missing, open JAR Manager under More, choose Fabric under Server software, and press Apply change. Change your Minecraft version or mod loader has the steps. Switching reinstalls the server and keeps your world, but the project asks you to back up your worlds, so use the Backups tab first.

Install C2ME

1. Open Mods, keep the Store view, and keep the Modrinth chip selected in the source chip row at the top of the tab.
2. Search for C2ME. Press Install on Concurrent Chunk Management Engine (Fabric). The NeoForge and OpenCL projects are separate results.
3. Restart the server from the Console tab.

Every C2ME build for Minecraft 26.3 on Modrinth is labelled alpha. The store takes the newest release, else the newest beta, else the newest alpha, so it installs the alpha build without further steps.

Check it started

Watch the Console during the restart. C2ME logs a line starting Global Executor Parallelism: that shows the thread count it configured and the default it worked out. In the Mods tab, open Installed and confirm C2ME has no Failed to load badge.

To see the effect, join and fly into terrain nobody has visited yet, since generation is what C2ME speeds up.

Mods it clashes with

C2ME's metadata declares conflicts with the mods dynview and betterchunkloading, and says it breaks tic_tacs and optifabric. Remove any of those before installing it. The project recommends running it with Lithium and ScalableLux; Install Lithium on your Minecraft server covers the first.

The config file

C2ME reads its settings from c2me.toml in the config folder. Its globalExecutorParallelism key sets the parallelism of the global executor, and the default is worked out from the machine's CPU count and memory. Leave it alone unless you have a reason. To change it, stop the server, edit the file in the File Manager, and start again.

Things to know

The project warns that vanilla world generation isn't deterministic, so worlds can differ run to run even with the same seed. It says this is not a C2ME bug. World generation datapacks that run on vanilla are fully supported. Mods that add their own world generators usually work, though they may hit compatibility problems.

Common problems

• It doesn't appear in the search: the Game version filter starts on your server's version. Each C2ME build is made for one Minecraft version, so a brand new version may not have one yet.
• The server won't start after installing it: read the Console for a conflict message, then see Fix mod and plugin errors on Minecraft.
• No change in TPS: something else is the limit. Why is my server lagging? Find the cause lists the usual causes.